Persistence of photosensitivity

Purpose: One hundred patients with photosensitive epilepsy were investigated as part of an ongoing follow-up study. Average duration of follow-up was 14 years; mean age at follow-up was 27 years. Methods: All patients were EEG investigated using a standard technique of intermittent photic stimulation (IFS). The presence of a photoparoxysmal response (PPR) or a degraded PPR indicated the presence of photosensitivity. Results: Seventy-seven patients became seizure free. Of the untreated patients, photosensitivity disappeared in 14 patients but was present in 32 patients. Of the patients who were treated, 31 showed evidence of PPRs or degraded PPRs, but 23 patients no longer showed evidence of photosensitivity. Thirty-two mothers had 67 children during the follow-up period. Thirteen have so far proved to be sensitive to IFS in the laboratory and four have also had photosensitive seizures induced in the outside environment. Nine of the children have been found not to be photosensitive nor have they had seizures. Conclusions: This study suggests that photosensitivity persists in at least two thirds of patients with photosensitive epilepsy and that valproate is effective in controlling this photosensitivity.